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SubjectRe: [PATCH v2 10/16] KVM: MMU: fask check whether page is writable
On 04/13/2012 01:14 PM, Xiao Guangrong wrote:
> Using bit 1 (PTE_LIST_WP_BIT) in rmap store the write-protect status
> to avoid unnecessary shadow page walking
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
> ---
> arch/x86/kvm/mmu.c | 40 ++++++++++++++++++++++++++++++++++------
> 1 files changed, 34 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 0c6e92d..8b71908 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -796,7 +796,9 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn)
> return level - 1;
> }
>
> -#define PTE_LIST_DESC (0x1ull)
> +#define PTE_LIST_DESC_BIT 0
> +#define PTE_LIST_WP_BIT 1
> +#define PTE_LIST_DESC (1 << PTE_LIST_DESC_BIT)
> #define PTE_LIST_FLAG_MASK (0x3ull)
>
> static void
> @@ -1067,6 +1069,12 @@ static bool rmap_can_add(struct kvm_vcpu *vcpu)
> return mmu_memory_cache_free_objects(cache);
> }
>
> +static void host_page_write_protect(u64 *spte, unsigned long *rmapp)
> +{
> + if (!(*spte & SPTE_HOST_WRITEABLE))
> + __test_and_set_bit(PTE_LIST_WP_BIT, rmapp);
> +}
>

Why is this needed, in addition to spte.SPTE_WRITE_PROTECT?

--
error compiling committee.c: too many arguments to function



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